Embodiments disclosed herein generally relate to inks. More specifically, embodiments disclosed herein relate to phase change inks that exhibit significantly improved scratch resistance compared to conventional inks. In particular, the inks disclosed herein exhibit significantly improved scratch resistance even at low temperatures.
Ink jet printing processes may employ inks that are solid at room temperature and liquid at elevated temperatures. Such inks may be referred to as solid inks, hot melt inks, phase change inks and the like. For example, U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing phase change ink for printing on a recording medium such as paper. In piezo ink jet printing processes employing hot melt inks, the phase change ink is melted by a heater in the printing apparatus and utilized (jetted) as a liquid in a manner similar to that of conventional piezo ink jet printing. Upon contact with the printing recording medium, the molten ink solidifies rapidly, enabling the ink to substantially remain on the surface of the recording medium instead of being carried into the recording medium (for example, paper) by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. Advantages of a phase change ink in ink jet printing are thus elimination of potential spillage of the ink during handling, a wide range of print density and quality, minimal paper cockle or distortion, and enablement of indefinite periods of nonprinting without the danger of nozzle clogging, even without capping the nozzles.
In general, phase change inks (sometimes referred to as “hot melt inks” or “solid inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jetting temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording medium, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops.
While numerous effective inks have been developed for phase-change digital printing in solid-ink-jet printing applications for their intended purpose, they may have limited utility in low temperature applications and/or may have high associated costs. A further continuing challenge in ink development is providing inks that exhibit significantly improved scratch resistance relative to current inks. This is especially the case when printing on paper or packaging employed at low temperatures, such as freezer bags, and the like, that may be handled many times.